DESCRIPTION (Applicant's Description) The goal of this project is to establish feasibility , and generate initial outcome data concerning the physical and psychological health benefits of a group exercise training program for postmenopausal women with newly diagnosed, nonmetastatic breast cancer. The project will determine whether a group exercise program can be an efficacious adjunctive intervention strategy for improving the health and quality of life of breast cancer patients. Postmenopausal women with primary breast cancer who provide informed consent will participate in a course of exercise training delivered in a structured group setting three times per week for 16 weeks. Assessment of fitness, well-being, and overall quality of life will be conducted prior to, during, and upon completion of the program, with follow-up assessment continuing for an additional 8 months (extending beyond the period of support provided by the grant itself). The specific objectives of this proposal are: (1) to demonstrate that the exercise training program can be efficacious for regaining cardiovascular fitness and muscular strength as well as controlling body weight following treatment for breast cancer; (2) to demonstrate that the exercise training program can enhance quality of life and well-being in the face of the physical and emotional distress that accompanies the diagnosis and treatment of breast cancer; and (3) to determine whether the beneficial physical and psychosocial effects of the group persist beyond the duration of the training program. Our immediate goal is to conduct a non-randomized, non-comparative trial to collect initial data concerning the feasibility and benefits of the exercise program, which if successful will support subsequent proposals to conduct randomized comparative trials. This project will provide important data for establishing guidelines for exercise training as a means to foster rehabilitation and enhance quality of life for postmenopausal women with breast cancer.